The invention is directed to a process for laying a nonwoven or the like according to the process presented in the claims and a nonwoven laying device for carrying out the process.
Nonwoven laying devices of the above type are used for laying nonwovens, fiber fleeces, spunbonded fabrics and the like, especially when delivered by a carding machine or the like, onto a discharge belt moved at a predetermined variable speed. In doing so, the nonwoven fiber fabric delivered by the carding machine is conveyed by a feed belt driven at a predetermined speed. Usually, within the nonwoven laying device, the nonwoven fiber fabric is at least partially transported between two conveyer belts moving at the same speed. These conveyer belts are provided as endless conveyer belts. For laying the nonwoven fiber fabric with maximum accuracy, nonwoven laying devices of the said type require reciprocating carriages having guide rollers for the conveyer belts arranged therein.
In nonwoven laying devices, particularly those operating at high speed, the sudden changes in speed of the carriages can result in uneven stretching of the nonwoven fiber fabric, caused by time differences in adjusting the speeds of the carriages and the conveyer belts due to the resilience of the frame and the working components.
Therefore, upon sudden acceleration of the conveyer belt, the nonwoven fiber fabric cannot follow up immediately. In nonwoven laying devices, it is essential that the conveyer belts and the carriages are controlled in such a manner relative to each other that the laying is effected with maximum uniformity.
In other known arrangements of nonwoven laying devices, the high acceleration rates upon reversal can be reduced by slowing down the process of reversal. These solutions, however, are disadvantageous because the nonwoven is supplied to the nonwoven laying device at a constant speed, and, necessitated by the coupled drive of the carriages, also has to be released at a constant speed. Thus, the reversal time must be theoretically zero which is practically impossible.
From EP-A-0 315 930, a nonwoven laying device is known wherein the upper carriage and the laying carriage have a common or also a separate drive for moving the carriages at different speeds in opposite directions. The upper carriage always moves at half the speed of the laying carriage and, in doing so, covers half the distance of the laying carriage. The drive is provided as a servo drive and is connected to a freely programmable control means. Therefore, the speed of the carriages can be changed as desired by setting their moving path, while also the acceleration periods in the reversal points of the traveling movement are variable as desired. The discharge speed of the nonwoven fiber fabric always corresponds to the intake speed of the nonwoven.
From FR-A-2 234 395, there is known a nonwoven laying device comprising an upper carriage and a laying carriage as well as a plurality of auxiliary carriages, wherein the upper carriage is reciprocated at a speed u while the laying carriage is reciprocated at a selectable speed w. The relation of the carriage speeds with respect to each other under consideration of the nonwoven supply speed V results from the equation 2.multidot.u-w+w=V. Due to this rule, no stuffing or stretching of the nonwoven shall occur. A variable setting of the speed relation between the upper carriage and the laying carriage is not described.
DE-A-26 09 396 discloses an endless rotating control chain coupling an upper carriage and a laying carriage and a storage carriage to each other. This endless rotating control chain is driven by chain wheels. Drive and control of the laying carriage, however, are performed by a separate carriage-drawing chain. Further, the laying carriage and the upper carriage are connected to each other by a tentering chain. Also, a measuring chain is required for the controlling.
Drive and control of this nonwoven laying device are very bothersome and nonetheless do not make it possible to set the stretching as desired.
From DE-18 21 234 U, it is known to couple the upper carriage and the laying carriage with each other by a power transmission element.
From DE-25 42 274 B, it is known to drive a laying carriage by a device operating according to the linear motor principle.